The invention is concerned with a ventilating, heating and/or air-conditioning apparatus for motor vehicles. This apparatus includes a fan located in a housing, a vaporizer for a cooling system, an afterheater or heating-system heat exchanger, a temperature-mixing air flap to steer the air flow to the after-heater, and connections for the admission of fresh air or recirculated air. Connections are also provided for the discharging of air into the passenger area, e.g., to the windshield, the defroster vent, the area occupied by the passenger's feet, etc.
A motor vehicle air-conditioning apparatus, of the type described above, is known from DE-OS No. 24 23 188, for example. In that prior art known apparatus, however, the fan is located in the flow path beyond the evaporator and/or after-heater in an arrangement including suction means, which produces disturbing fan noises in the inner space of the vehicle. In another known air-conditioning apparatus for motor vehicles (U.S. Pat. No. 3,809,151) including at least one heat exchanger serving as a cooling element and another serving as a heating element and located in a series connected air-duct system, through which air is conducted to the inner space of the vehicle, the temperature in the vehicle is influenced by a vane assembly. This assembly mixes the air flowing through three parallel air ducts in an appropriate manner. The air is preferably heated in one air duct and cooled in the second air duct, while the temperature of the air flowing through the third air duct is unchanged.
In an air-conditioning apparatus of the kind just described above, two streams of air, at the most, are always mixed with each other; one of those streams is the stream of air the temperature of which corresponds to that of the outside air.
Providing a by-pass for the fresh air, which encircles the heating-system heat exchanger, is also known (DE-AS No. 16 55 121) in a heating and ventilating apparatus for a motor vehicle. In that apparatus at least one control flap to steer the quantity of fresh air flowing through the by-pass is provided and the by-pass stream of air strikes the stream of air conducted through the heating element almost at right angles. No evaporator is provided in this known apparatus.
However, passenger-space air-conditioning apparatuses are also known (U.S. Pat. No. 4,072,186) in which cooled air from the evaporator can be conducted to the passenger space over a mixing flap after subjection to a heating element. In such apparatus, conducting of moist air from the evaporator to the passenger space, the air being first dehumidified and then heated by the heating element (reheat system) is made possible.
Other heating, ventilating and/or air-conditioning apparatuses of various kinds of design, as well as components of such systems, are known from U.S. Pat. No. 3,948,312, British Pat. No. 1,508,908 and British Pat. No. 1,539,902.
In accordance with the known state of the art, the adjusting and controlling of air-conditioning apparatuses for motor vehicles is accomplished to permit varying amounts of air to flow through their afterheaters. The evaporator is adjusted by a simple two-point adjustment of the evaporator fin surface temperature by turning the compressor drive on or off and the afterheater is adjusted by constant adjustment of the afterheater output with constant adjustment of air-mixing flaps. In such apparatus, frequent variation in temperature of the air beyond the evaporator results from turning the compressor on and off and causes varying disturbance on the subsequent section of the afterheater, which is constantly being adjusted and is thus stimulated to oscillate. This oscillation phenomenon is especially critical where there is a slight afterheating output, only a small amount of air flows through the afterheater and the temperature amplitude of the heated air remains practically undamped.
The temperature variations in the air exhausts of 4.degree.-5.degree. K. are passed on, up to approximately 50%, to the inside air and are detected by a sensitive NTC resistance thermometer which measures the temperature of the inside air. That resistance reading logically results in a frequent readjustment of the afterheater.
The known air-conditioning apparatuses also have generally unfavorably-designed secondary-air flaps, which are required in the partial-load area to mix a small amount of air, which is heated to approximately 85.degree. C., with a relatively large amount of air which is conducted past the heat exchanger and is at about 5.degree. C., for example. As a result, considerable differences in air temperature appear at the vents of the air-conditioning apparatus, even inside an air exhaust. Tension symptoms and discomfort of passengers are intensified if the speed of motor vehicle travel is increased; specifically, the atmospheric pressure at the air intake in front of the windshield increases and the amount of air passing through the interior of the vehicle rises to a multiple of the desired amount.
A vertical temperature variation occurs in the interior vehicle space, in connection with air-conditioning apparatuses characterized by higher temperatures existing at passenger breast heights and lower temperatures at the passenger head elevations. This frequently causes tension symptoms in passengers which result from unduly low temperatures at the head level of the passenger resulting from an unduly high velocity of air flow through the interior of the vehicle.
An object of the present invention is to create a downstream controlling or regulating system including provision of adjustable temperature gradients for the air exhausts and an adjustable degree of dehumidification for the air contacting the vaporizer in a ventilating, heating or air-conditioning apparatus. In such a system, all air discharge temperatures, in particular, are to be maintained uniform and the amount of air flowing through the system is to be kept nearly constant, independent of the speed of travel of the vehicle or the speed of the air blown by the fan.
Essentially, this object is accomplished by the invention by providing the evaporator with a fixed air deflector constituting an outlet duct and a by-pass duct and providing a movable first temperature-mixing air flap with a movable air-volume-regulating flap. These flaps are moved between a limiting position closing off the evaporator outlet and a limiting position closing off the by-pass duct. An afterheater is provided with a fixed air deflector on the approach-flow side and a deflector of the downflow side to constitute an intake duct, an outlet duct and a by-pass duct. A movable second temperature-mixing air flap is provided with a limiting position closing off the intake duct into the afterheater and a limiting position closing off the by-pass duct. Thus the evaporator and afterheater, downstream, either in their cooling or afterheating air output, are adapted to be controlled either independently of each other or in a definite preselected functional linkage with one another.
It is especially advantageous that, in accordance with another feature of the invention, each temperature-mixing air flap is hinged to the lower end of the evaporator or afterheater.
In a preferred embodiment of the invention, the flow cross sections of the by-pass ducts have dimensions which are the same as those of the hot-air and cold-air ducts functioning as diffusers by the action of air deflectors which are associated with them.
In an advantageous further development of the invention, the air deflectors constitute a duct assembly which conveys cold air and leads directly to a discharge area constituting middle vents and lateral vents in the car interior.
In still another development, it is advantageous that an air flap be provided to control the amount of cold air flowing through the discharge outlet for cooled air (air-conditioning outlets).
In a further development of the invention, it is advantageous that the air-volume-regulating flap be adapted to swivel between the air deflector and the wall of the housing and have a shape which conforms to the housing wall, which is located in that area.
In particular, it is advantageous that the air-volume-regulating flap have a means of controlling the electric voltage for the fan which depends upon the angle of rotation of the air-volume-regulating flap.
A preferred embodiment of the invention is characterized in that the air deflector and the by-pass duct to the evaporator, on the one hand, and the air deflector and the by-pass duct to the afterheater, on the other, are arranged so that the cold air strikes the warmer air from the by-pass duct to the evaporator at right angles beyond the evaporator (from the cold-air duct). Moreover, the hot air of the hot-air duct should strike the colder air flowing through the by-pass duct to the afterheater at right angles beyond the afterheater.
To make the air temperature at the individual discharges uniform, it is advantageous if a rerouting section is provided beyond the hot-air duct or the by-pass duct to the afterheater and an air mixing area is provided therebeyond.
For that purpose, it is also advantageous to locate the air discharges for the area occupied by the passengers' feet, the defroster, the middle vents and the lateral vents in an arrangement, one after the other beyond the air mixing area, in accordance with the desired temperature gradients.
An advantageous method of constructing the temperature-mixing air flaps, from the point of view of operational techniques, results when the air deflectors have lateral parts which run in a tapering direction with respect to the air deflectors, from the points where they are fastened to the heat exchangers, and the hoods formed in that way are separated laterally from the housing wall.
It is especially advantageous for the temperature-mixing flaps to be fitted to the trapezoidal intake and outlet cross sections of the hoods, which are formed, and thus have no sealing function to perform with respect to the housing wall, so that a torsional moment which is as small as possible is ensured.
An apparatus constructed in accordance with the invention is characterized in that the air temperature variations, as a result of two-point adjustments of the compressor of approximately 4.degree.-5.degree. K. at the air exhausts in the partial-load area of the air-conditioning operation, which are caused by the temperature-mixing air flap at the vaporizer, are cut approximately in half. The air deflectors, which are located after the heat exchangers evaporator and afterheater), cause the volume of air from the evaporator and the afterheater to strike the volume of air being conveyed in either by-pass approximately at right angles in the partial-load area. As a result, an optimal mixing of those two volumes of air is achieved.
Since the flow cross sections of each by-pass duct are equal to or, at a maximum, 10% smaller in size than the flow cross sections between the corresponding heat exchangers (air exhaust sides) and air deflectors that are associated with them, the quantity of air flowing through each heat exchanger (evaporator or afterheater) in the intermediate position of the temperature-mixing air flaps is made approximately equal in volume to the quantity of air which flows through the corresponding by-pass. As a result, a linearization of the characteristic curve for the temperature-mixing air flap is obtained, at least in the middle range.
The duct having the air deflectors on the downflow side of the evaporator and on the approach-flow side to the afterheater, which leads directly to the air-conditioning exhausts, makes it possible for an adjustable volume of cold air flow in the channel, depending upon the position of an air flap which is attached to that duct. Thus the air emerging at the air-conditioning exhausts can be altered in temperature from quite cold to the temperature of the other exhausts.
The drop in pressure is kept as small as possible by the passages for conveying air, which are built in accordance with the invention, and also by the air deflectors.
Because of the special way the deflectors and temperature-mixing air flaps are constructed, the latter do not have any sealing functions to perform with respect to the lateral walls of the housing and the torsional moment is minimal and almost equally large for all temperature-mixing air flaps.
In another embodiment, which is a further development of the invention, it is advantageous to have means for controlling the automatic adjustment of the air-volume-regulating flap, which means are dependent upon the atmospheric pressure and also dependent upon the speed of vehicle travel, so that the rate of air flow remains nearly constant.
It is also advantageous to include means for controlling the continuous adjustment of the first temperature-mixing air flap, depending upon the temperature of the outside air, the temperature of the air inside and the humidity of the air to be provided which, by means of a regulating device, makes constant adjustability possible.
Furthermore, it is advantageous to include means for controlling the adjustment of the degree of dehumidification and cooling of the volumes of outside air passing through the ducts. Desired values for a vaporization temperature regulator or a vaporization pressure regulator and/or the electric voltage for the fan should also be adjustably controlled.
It is desirable for the evaporator pressure regulator or evaporator temperature regulator to be functionally linked to the first temperature-mixing air flap in such a way that the desired value of that regulator is constantly set higher as the air volume through the evaporator decreases. Also, the compressor should be switched off in a known manner by using a magneto coupling when a maximum value of air flow through the evaporator is reached. The compressor should be correspondingly switched on when this air flow is reduced below a predetermined value.
It is advantageous for the temperature-mixing air flap of the afterheater to be adjusted automatically in conformity with the temperature of the outside air and the temperature of the inside air and to be coupled functionally with the drive mechanism for the temperature-mixing air flap of the evaporator in such a way that an adjustment takes place. However, a desired value for the degree of dehumidification and cooling is accomplished by an adjustment only of the temperature-mixing air flap of the evaporator.
It is advantageous for the individual air discharges to be provided with air valves, which are activated by motors, especially for the space occupied by the passengers' feet. The lateral vents can be adjusted separately, in at least two stages, for each side of the vehicle, and in that way make it possible to admit different amounts of air on the driver's side and on the opposite side.
Finally, it is desirable, in another further development of the invention, for the air-conditioning apparatus to include a control device for remotely controlling the vanes which are either controllable individually or are functionally linked for manual control. This device is particularly useful for setting the desired values for the quantity of air, the inside temperature of the air and the degree of dehumidification of the air, which is admitted into the vehicle.
It is desirable for the air valves activated by motors to be linearly-displaceable poppet valves. Pneumatic servomotors (vacuum adjustment boxes), with their activating rods being connected flexibly with the poppet valves, can provide the driving force for the mechanism.
Such poppet valves are familiar in connection with cold-water and hot-water circuits (DE-AS No. 19 16 640).
Additional details concerning and advantages of the invention are described more fully in conjunction with the embodiments, which are represented schematically in the drawings.